Electronic article surveillance (EAS) systems are known in which dual status EAS tags are attached to articles to be monitored. One type of dual status EAS tag comprises a length of high permeability, low coercive force magnetic material which is positioned substantially parallel to a length of a magnetizable material used as a control element. When an active tag, i.e. one having a demagnetized control element, is placed in an alternating magnetic field, which defines an interrogation zone, the tag produces a detectable valid tag signal. When the tag is deactivated by magnetizing its control element, the tag may produce a detectable signal which is different than the detectable valid tag signal.
Methods and apparatus for magnetizing the control element, thereby deactivating the tag, are described in U.S. Pat. No. 4,684,930. In the '930 patent, a series of permanent magnets are arranged on a convex curved outer surface of a rotatable cylinder. To deactivate the tag, the tag is rolled over the outer surface of the rotatable cylinder so that the permanent magnets of the cylinder come closely adjacent to and thereafter move away from the tag. In this way, the control element of the tag is magnetized.
The deactivating device of the '930 patent is mechanically complex in that the permanent magnets must be mounted on the outer surface of the cylinder and the cylinder must be mounted so as to freely rotate. After repeated deactivation operations, due to repeated mechanical contact with the tags, the outer surface of the cylinder is subject to wear. Still further, the deactivating device of the '930 patent requires operator intervention to effect the deactivation of the tag (i.e., the operator moving the tag over the deactivating device to rotate the cylinder.) Accordingly, the deactivation device of the '930 patent does not easily lend itself to an automated deactivation process.
A deactivation device is known which uses an electromagnet, which when energized forms a deactivating electromagnetic field in a deactivation area to magnetize the control elements of tags placed therein. Such deactivation devices are currently used in, for example, library EAS systems. In such library systems, a photocell is arranged to detect the presence of a book in the deactivation area. Responsive to the detection by the photocell, the electromagnet is energized thereby producing the deactivating electromagnetic field. The photocell advantageously prevents the electromagnet from being continuously energized thereby reducing the power consumption of the deactivation device.
In the above deactivation technique, while the photocell detects the presence of a book in the deactivation area, such detection does not indicate whether a tag is attached to the book. Further, in the case where a tag is attached to the book, the detection by the photocell fails to indicate whether the tag is active or deactivated. Accordingly, the electromagnet will not only be energized when a book having an active tag is placed in the deactivation area, but will also be energized when a book without a tag, or with a deactivated tag, is placed in the deactivation area.
When using a deactivating electromagnetic field to deactivate tags, for proper deactivation to occur the tag must be passed through the deactivation area in a proper orientation relative to the deactivating electromagnetic field. However, in the above technique using a photocell, the photocell only detects the presence of the book and fails to detect the presence or orientation of an attached tag. Accordingly, the deactivating electromagnetic field is formed even when the tag is not properly oriented for effective deactivation within the deactivation area.
It is, therefore, a primary objective of the present invention to provide an improved device for detecting and deactivating dual status type tags of an EAS system.
It is a further object of the present invention to provide an improved deactivation device in which the orientation of a deactivating field for deactivating a tag substantially matches a detection field for detecting the presence of a tag.
It is still a further object of the present invention to provide a deactivation device incorporated into a checkout apparatus for deactivating tags.